Unsaturated melamine condensates

ABSTRACT

An unsaturated condensate of an alkoxymethylmelamine, an allylic alcohol and an acrylamide wherein the alkoxymethyl group contains from 1 to 4 carbon atoms, wherein the ratio of allylic moieties to acrylamide moieties is in the range of about 3:1 to about 1:3, wherein there is at least about 0.75 allylic moieties and no more than about 3 acrylamide moieties per melamine ring and wherein the total of allylic moieties and acrylamide moieties is in the range of about 2 to about 4 per melamine ring. The unsaturated condensates are used in high solids unsaturated coating systems containing unsaturated oil-modified resins.

This invention relates to unsaturated melamine condensates obtained fromcondensation of an alkoxymethylmelamine, an allylic alcohol and anacrylamide and to a process for the preparation of such condensates.More particularly it is directed to condensates of analkoxymethylmelamine, allyl alcohol and acrylamide and a process for thepreparation of such condensates.

Anti-pollution legislation has caused the coatings industry to seek highsolids coatings. Alkyd manufacturers have tried to increase thesolids/viscosity ratio of their products by reducing the molecularweight of the alkyd. While this approach has been successful in raisingthe solids of air dry alkyd paints, it has produced some undesirableside effects in the resulting coatings; namely, lower hardness, solventresistance and water resistance, and longer tack free and cure times.The use of conventional aminoplast crosslinkers fails to improve theseproperties in air dry alkyd coatings.

The present invention provides unsaturated melamine condensates whichare useful as crosslinkers of unsaturated oil-modified resins such asthose used in high solids alkyd coatings, allowing them to be air-driedto hard, solvent and water resistant coatings. The unsaturated melaminecondensates are prepared by condensing an alkoxymethylmelamine, anallylic alcohol and an acrylamide to provide a condensate wherein theratio of allylic moieties to acrylamide moieties is in the range ofabout 3:1 to about 1:3, wherein therein is at least about 0.75 allylicmoieties and no more than about 3 acrylamide moieties per melamine ringand wherein the total of allylic moieties and acrylamide moieties is inthe range of about 2 to about 4.0 per melamine ring. Another aspect ofthe invention is directed to a process for the preparation of thecondensates which comprises reacting an acrylamide with analkoxymethylmelamine at a temperature below about 120° C. until thereaction is substantially complete and then reacting theacrylamidealkoxymethylmelamine with an allylic alcohol at a temperaturein the range of about 90° to about 110° C. in the presence of acatalytic quantity of an acid catalyst and a polymerization inhibitingquantity of an inhibitor.

The alkoxymethylmelamine is a methylolated, etherified melamine obtainedby reaction of formaldehyde and melamine under conditions well known inthe art to minimize the amount of oligomerization which can occur whenmethylene or methylene ether bridges are formed by intercondensation ofmethylol groups, followed by etherification with an alcohol or mixtureof alcohols. The combined ratio of formaldehyde to melamine in thealkoxymethyl melamine is in the range of about 5:1 to about 6:1 and thecombined ratio of the etherifying alcohol is in the range of about 4.7to about 6.0 moles per mole of melamine. The etherifying alcohol isselected from the group consisting of methyl, ethyl and isopropylalcohols, and mixtures thereof and mixtures with higher alcoholscontaining up to 10 carbon atoms. However the amount of methoxy, ethoxyor isopropoxy groups should at least be stoichiometric with the allylicalcohol and acrylamide condensing agents to allow ready displacement ofalkoxy by the allylic and acrylamide groups. The preferred etherifyingalcohol is methyl alcohol because its volatility and low boiling pointallow its more ready displacement from the alkoxymethylmelamine. Theaverage degree of oligomerization of the alkoxymethylmelamine is threeor less and is preferably less than two.

The acrylamide which is condensed with the alkoxymethylmelamine can berepresented by the formula: ##STR1## where R₁ and R₂ are selected fromthe group consisting of H and methyl. The preferred acrylamide isacrylamide.

The allylic alcohol which is condensed with the alkoxymethylmelamine canbe represented by the formula: ##STR2## where R₃ is hydrogen or a C₁ toC₄ alkyl group. The preferred allylic alcohols are allyl alcohol andmethallyl alcohol.

The ratio of allylic moieties to acrylamide moieties in the unsaturatedmelamine condensate is in the range of about 3:1 to about 1:3 so thatwhen the unsaturated melamine condensate is incorporated intounsaturated alkyds it can reduce the viscosity of the system withoutsubstantially increasing the time required by the system to reach atack-free state when it is allowed to dry in air. In general the allylicmoieties promote a reduction in viscosity of the system, the acrylamidemoieties enhance the hardness of the air-dried coating and theacrylamide and allylic moieties together enhance the drying properties.There should be at least about 0.75 allylic moieties in the unsaturatedmelamine condensate and no more than about 3 acrylamide moieties and thetotal of allylic moieties and acrylamide moieties should be in the rangeof about 2 to about 4.0 per melamine ring. More preferably the number ofallylic moieties per melamine ring is in the range of about 1 to about 3and the number of acrylamide moieties per melamine ring is in the rangeof about 1 to about 2 to provide a balance of viscosity reduction andrate of air-drying to an unsaturated alkyd system and even morepreferably the number of allylic moieties is in the range of about 1.5to about 2.5 and the number of acrylamide moieties is in the range ofabout 1 to about 2.

The unsaturated melamine condensate of the present invention can beprepared by the stepwise reaction of the allylic alcohol and theacrylamide or the acrylamide and the allylic alcohol with thealkoxymethylmelamine. Preferably the acrylamide is reacted in a firststep with the alkoxymethylmelamine and the allylic alcohol is reacted ina second step. If the allylic alcohol is reacted in a first step,reaction of the acrylamide in the second step causes some of the allylicalcohol to be displaced by the acrylamide during the reaction, reducingthe efficiency of the reaction and tending to form high molecular weightmaterials. When the acrylamide is reacted in the first step, nodisplacement of the acrylamide by the allylic alcohol is observed in thesecond step. An undesirable method of carrying out the reaction isrealized when the alkoxymethylmelamine is reacted simultaneously with amixture of the allylic alcohol and the acrylamide instead of by stepwisereaction. Unexpectedly, an acrylamide by-product is formed and gelationof the unsaturated melamine tends to occur.

In the reaction of the acrylamide with the alkoxymethylmelamine, thetemperature is maintained below about 120° C. to minimize polymerizationreactions and in the initial stage of the reaction the temperature ispreferably maintained below about 90° C. while the methanol generated bythe condensation reaction is removed under reduced pressure. In thesecond stage of the reaction, an excess of allylic alcohol is added tothe alkoxymethylmelamine/acrylamide condensation product and thetemperature is gradually increased in the range of about 80° to about110° C. while the methanol reaction product is slowly distilled atatmospheric pressure through a multiplate distillation column. When thedesired degree of replacement of methyl with allylic groups has occurredthe reaction medium is distilled under reduced pressure to removeresidual methanol and unreacted allylic alcohol. It is then convenientto add a small quantity of a suitable solvent to the melamine condensateto inhibit a tendency to crystallize which can occur particularly withcondensate containing higher levels of acrylamide groups.

The reaction of the alkoxymethylmelamine and the acrylamide is carriedout in the presence of a catalytic amount of an acid catalyst selectedfrom the group consisting of protonic acids of pKa less than about 2 andLewis acids. A catalytic amount is an amount which allows the reactionto be completed within a reasonable time, usually less than 24 hours ata selected temperature. The catalyst is generally added in an amount offrom about 0.1 to about 5 weight percent, preferably from about 0.5 toabout 2 weight percent of the reaction mixture. The protonic acids canbe selected from the mineral acids hydrochloric, nitric and sulfuricacids, organic acids such as formic acid and oxalic acid, and sulfonicacids such as methane sulfonic acid, trifluoromethane sulfonic acid,benzene sulfonic acid and p-toluenesulfonic acid. The sulfonic acids aregenerally preferred since they are strong acids, readily soluble in thereaction medium and can be readily added without the addition of water.The Lewis acids can be selected from the group consisting of metalhalides such as stannic chloride, aluminum chloride, ferric chloride andmagnesium bromide, metal alkoxides such as aluminum isopropoxide,tetrapropyl titanate, tetrabutyl zirconate, and dipropyl diacetonyltitanate, metal salts of organic acids such as stannous octoate, stannicoctoate and dibutyl tin diacetate, and boron compounds such as borontrichloride, boron trifluoride and boron trifluoride etherate. For highconversion, boron trifluoride, aluminum chloride and stannic chlorideare among the preferred Lewis acids.

To prevent premature polymerization of the unsaturated melaminecondensate or the acrylamide during the condensation reaction, apolymerization inhibiting quantity of an inhibitor of free radicalpolymerization is added to the reaction mixture. Excess of inhibitorshould be avoided since it can inhibit the polymerization of air-dryingunsaturated oil-modified resins containing the unsaturated melaminecondensate of the present invention, causing an excessively longinduction period when the compositions are air-dried. Effectiveinhibitors include hydroquinone, ethers of hydroquinone, and quinone.

The unsaturated melamine condensates can be used with unsaturatedvehicles to reduce the viscosity of coating systems containing suchvehicles, and to improve the drying properties and hardness of thecoatings. The condensates are especially useful with air-dryingunsaturated or oil-modified resins of molecular weight about 10,000 orless and glass transition temperature in the range of about 0° to about100° C. having an oil length in the range of about 15 to about 50%. Theoil modified resins can be oil modified alkyd resins prepared fromconventional polybasic acids, polyhydric alcohols and oil-modifyingfatty acids, or oil-modified styrene allyl alcohol copolymers preparedby esterification of styrene allyl alcohol copolymers containing fromabout 2 to about 10 hydroxy groups per molecule with oil modifying fattyacid, or oil modified acrylic resins prepared by esterification of oilmodifying fatty acid and low molecular weight hydroxy containing acryliccopolymrs of glass transition temperature of about 25° C. or higherprepared by interpolymerization of C₄ to C₇ alkyl acrylates or C₅ to C₈alkyl methacrylates with a hydroxy monomer selected from the groupconsisting of allyl alcohol, methallyl alcohol, and C₅ to C₈ hydroxyacrylates or hydroxy methacrylates such as 2-hydroxyethyl acrylate and2-hydroxyethyl methacrylate, or oil-modified epoxy resins prepared byreaction of an oil-modifying fatty acid with an epoxy resin condensateof the diglycidyl ether of bisphenol A or an epoxidized polybutadiene.Preferred oil-modified resins are of molecular weight in the range ofabout 500 to about 8000, and glass transition temperature in the rangeof about 20° to about 60° C. and contain an oil modifying fatty acidcomprising at least about 60 percent by weight of a polyunsaturatedfatty acid such as linoleic or linolenic acid.

It is desirable that the oil or fatty acid modifying agent shouldcontain at least 60% by weight, preferably at least 80% by weight, of apolyunsaturated fatty acid such as linoleic acid or linolenic acid,based on the total fatty acid content. Accordingly, the fatty acidswhich may be used in the present invention are fatty acids separatedfrom drying oils or semi-drying oils such as dehydrated castor oil fattyacid (a linoleic acid content of 76 to 88%), linseed oil fatty acid (alinoleic acid content of 15% and a linolenic acid content of 52%) andsafflower oil fatty acid (a linoleic acid content of 72 to 80%) as wellas linoleic acid, linolenic acid and a mixture of the both. In thepreparation of the oil-modified resins it is generally desirable to adda sufficient amount of a polymerization inhibitor such as hydroquinoneto inhibit gelation during the reaction.

Unsaturated oil modified resin compositions in combination with theunsaturated melamine condensates can contain from about 50 to about 90parts by weight of the unsaturated oil-modified resin and from about 50to 10 parts by weight of the unsaturated melamine condensate. Preferablythe combination contains from about 70 to about 90 parts by weight ofthe unsaturated oil-modified resin and from about 30 to about 10 partsby weight of unsaturated melamine condensate. Too high levels of theunsaturated melamine condensate can cause longer times to reach atackfree condition and deterioration of properties such as flexibilityin the cured coating especially when the condensate contains high levelsof acrylamide. When the level is too low no appreciable effect on theviscosity of the coating composition and the hardness and solventresistance of the coating is obtained.

The air-drying compositions of the present invention comprisingunsaturated alkyds and unsaturated melamine condensates may beformulated in any of the conventional solvents for such systemsincluding aromatic hydrocarbons, aliphatic esters, and aliphtic ketonesand mixtures thereof and mixtures containing aliphatic hydrocarbons. Thesolutions can be used at any dilution which is convenient forapplication of the coating compositions to a substrate. Preferably thesolids of the coating compositions are greater than 50 weight percentand even more preferably 70 percent or greater since advantage can betaken of the ability of the unsaturated melamine condensate to reducethe viscosity of higher molecular weight unsaturated oil-modified resin.

The air-drying compositions containing unsaturated oil-modified resinsand the unsaturated melamine condensates may be cured at roomtemperature by means of metal dryers of heavy metals such as cobalt,manganese and zinc salts of naphthenic acid, neodecanoic acid and thelike or by means of such metal dryers in combination with the alkalimetal salts of these acids. When the coating compositions are used asroom-temperature drying paints, they are suitable for painting outdoorstructures, and heavy machinery and equipment too bulky to be passedthrough drying ovens.

The unsaturated air-drying compositions may also be force-dried andcured at elevated temperatures of up to about 100° C. and more and suchcure may be accelerated by conventional free radical catalysts such asperoxides and hydroperoxides and by redox systems such as benzoylperoxide and dimethylaniline.

The coating compositions can be modified by the addition of pigments,plasticizers, colorants, dyes, pigment dispersing agents, flow controlagents, stabilizers and the like.

Other types of unsaturated vehicles which may be usefully combined withthe unsaturated melamine condensates are polyesters containing internalunsaturation derived from maleic acid moieties and the like and pendantunsaturation provided by allylic or acrylic groups. Such polyestercompositions are conveniently cured by free radical methods at elevatedtemperatures, and can include significant amounts of vinyl monomers suchas acrylates, methacrylates and aromatic vinyl monomers such as styrene.

The following examples are set forth in illustration of the inventionand should not be construed as a limitation therof. Unless otherwiseindicated, all parts and percentages are by weight.

EXAMPLE 1

This example describes the preparation of an unsaturated melaminecondensate containing 1.5 acrylamide units and 1.5 allyl units permelamine ring.

To a kettle equipped with stirrer, thermometer, heating jacket and avacuum outlet are charged the following:

1024 parts Hexamethoxymethyl melamine

300 parts Acrylamide

3.24 parts Methane sulfonic acid

0.60 parts Hydroquinone (0.2% by wt. on acrylamide)

0.30 parts Quinone (0.1% by wt. on acrylamide)

The above are stirred as the temperature is increased to 80° C. At 80°C., a vacuum of 380 mm mercury is applied. The temperature and vacuumare slowly increased to 110° C. and 50 mm Hg Vac, respectively, until 99percent of the acrylamide has reacted. This generally requires 3 hoursfrom start to finish.

At this point, the temperature is reduced, the vacuum outlet is closedand the kettle is connected to a 10 plate Oldershaw fractionationcolumn, and 488 parts allyl alcohol is added to the reaction product.The reaction temperature is gradually increased from 85° C. to 102° C.as 126 parts methanol corresponding to insertion of 1.5 allyl groups permelamine, is removed. At this point the reaction mixture is neutralizedwith 50% caustic (NaOH) and the unreacted allyl alcohol and any othervolatiles are removed by vacuum distillation at 110° C. and 50 mmmercury vacuum. The product is cooled to about 80°-85° C. whereupon2-butanone (methyl ethyl ketone) is added to produce a 78.4% by weightsolids product. This product is filtered through a bed of Celite beforeuse.

EXAMPLES 2-8

By the procedure of Example 1, the following examples containingdifferent proportions of acrylamido moieties and allyl moieties areprepared from hexamethoxymethylmelamine, acrylamide and allyl alcohol.

                  TABLE 1                                                         ______________________________________                                        UNSATURATED MELAMINE CONDENSATES                                                        Allyl groups Acrylamide groups                                      Example   per melamine ring                                                                          per melamine ring                                      ______________________________________                                        1         1.5          1.5                                                    2         2.5          1.5                                                    3         0.75         1.5                                                    4         2            2                                                      5         0            1.5                                                    6         0            2                                                      7         1            2                                                      8         3            0                                                      ______________________________________                                    

EXAMPLE 1A

An air-drying resin composition is prepared by blending 1200 parts byweight of a 70 percent xylene solution of an oil modified unsaturatedresin (M.W. 6000, oil length 35), 268 parts of the unsaturated melaminecondensate solution of Example 1, 6 parts of a 12% solution of cobaltneodecanoate, 12 parts 18% lithium drier sold by Tenneco Inc. under thetradename LTD drier and 32 parts of methyl ethyl ketone. The resultingmixture is stirred until a homogeneous product results. This formulationis 70% by weight total solids and contains an 80/20 w/w solids ratio ofoil-modified unsaturated resin to unsaturated melamine condensate. Theviscosity of this formulation is 2500 cps at 25° C. The coatingcomposition is applied to 0.64 mm Bonderite 37 steel panels and dried inair.

The following procedures are used to evaluate the coating composition:

Viscosity is determined by Brookfield Viscometer and Gardner-HoltViscosity tube comparison at 25° C.

Formulation stability is determined by storing the formulations in clearGardner-Holt viscosity tubes and/or in sealed 57 ml. jars (clear) atroom temperature. The formulations are exposed to light and areperiodically examined for any skin formation and/or viscosity change.

Coating thicknesses on steel panels are determined by means of a GEthickness Gage Type B Model A 337AY2.

Tack free times are determined in two ways:

(A) When the finger with a slight pressure will not leave a mark and thesurface is not sticky to the touch.

(B) A strip of aluminum foil, approx. 19 mm×76 mm, is smoothed andcurled into a "C" shape by drawing the strip between a flat surface anda glass tube. One end of this curled foil strip is placed on the coatingand held in place for 8 seconds with a 17 gram weight. If the foil rollsover when the weight is removed, the coating is judged tack free.

Coating hardness is determined by the standard pencil hardness testingprocedure (ASTM D3363-74).

Solvent Resistance is determined by rubbing a felt tipped marker, thetip of which is saturated with methyl ethyl ketone, over the curedcoating and determining the number of rubs necessary to penetrate ordissolve the coating, exposing the bare metal substrate. A single rubconstitutes moving the MEK saturated marker across the coating and backover the same path to the starting point.

Water spot test. A pool of water, about 12 mm in diameter, is placed onthe cured coating and covered with a watch glass. After 30 minutes atroom temperature, the glass cover is removed, the water is removed, andthe hardness of the exposed portion of the coating is immediatelydetermined by the standard pencil hardness test described above. Anywhitening or other changes in the film appearance (e.g. blistering,swelling, etc.) are also noted.

Coating flexibility is determined by means of the Gardner Falling DartImpact Tester. Failure was occurred when the coating shows any sign ofcracking or crazing.

Durability is determined by exposing coatings on steel substrates to theweatherability cycle of the QUV Accelerated Weathering Tester (Q-PanelCompany). Each cycle consists of 8 hours of condensation at 60° C.followed by 16 hours of ultraviolet at 65° C.

Data from the evaluation of Example 1A are presented in Table 2.

EXAMPLES A-SERIES

Air-drying compositions are prepared from the unsaturated melaminecondensates of examples 2-6 by the formulation of example 1A to providea series of coating compositions containing unsaturated oil-modifiedresin and unsaturated melamine condensate in the weight ratio of 80parts to 20 parts. Data for the evaluation of the coating compositionsare presented in Table 2 along with data for Example 9A comprising theunsaturated resin without the unsaturated melamine condensate. The datashow that the mixed unsaturates i.e. the melamine condensates containingboth allyl and acrylamide units in Examples 1A, 2A, 3A and 4A causesignificant decrease in viscosity of the coating system and improve thehardness, solvent resistance and water resistance of the coatingswithout adverse effect on the impact resistance and the tack free timewhile the unsaturates containing only acrylamide units have littleeffect on hardness, solvent resistance or water resistance and increasethe tack free time substantially.

                                      TABLE 2                                     __________________________________________________________________________    Evaluation of Air-drying Unsaturated Compositions, A Series                                Example                                                                             Example                                                                              Example                                                                              Example Example                                                                              Example                                                                              Example                Sample Number                                                                              1A    2A     3A     4A      5A     6A     9A                     __________________________________________________________________________    Formulation Appearance                                                                     hazy  sl. hazy                                                                             hazy   hazy    sl. hazy                                                                             sl. hazy                                                                             clear                               purple                                                                              purple purple purple  purple purple purple                 Formulation Visc. (cps)                                                                    2400  2300   2500   2400    2350   2300   7500                   Formulation Shelf Stab.                                                                    skin 1 day                                                                          skin 1 day                                                                           skin 1 day                                                                           skin 1 day                                                                            skin 1 day                                                                           sl. skin                                                                             skin 1 day                          sl gel 3 wk                                                                         mod gel 3 wk                                                                         no gel 3 wk                                                                          sl gel 3 wk                                                                           no gel 3 wk                                                                          no gel 3                                                                             no gel 3 wk            Coating Thickness (mm)                                                                     .038  .038   .038   .038    .036   .036   .038                   Tack Free Time* (min)                                                                      110/120                                                                             135/145                                                                              95/105 105/115 150/230                                                                              160/210                                                                              75/95                  Hardness                                                                            1 day  6B-   <6B    <6B    <6B     <6B    <6B    <6B                          2-3 days                                                                             3B    4B     2B     3B      3B     2B     5B-6B                        10 days                                                                              F-    F-     F-     F-      B      B      B-                           21 days                                                                              F     F-HB   F-     F-      HB+    HB-    B                      MEK rubs                                                                            2-3 days                                                                             62    87     48     61      50     45     22                           10 days                                                                              200   200    120    160     95     75     40                           21 days                                                                              200   200    160    200     110    95     43                     Water Spot                                                                          3 days ↓5B                                                                          ↓5B                                                                           ↓5B-                                                                          ↓5B                                                                            ↓4B                                                                           ↓4B                                                                           ↓6B                   10 days                                                                              ↓HB-                                                                         ↓HB-                                                                          ↓B                                                                            ↓B-                                                                            ↓3B                                                                           ↓2B                                                                           ↓4B             Forward Impact 21 days                                                                     1.6   1.3    1.5    1.5     1.0    1.1    1.5                    QUV Durability 21 days                                                                     joules                                                           1 day exposure                                                                             dense PH                                                                            dense PH                                                                             dense PH                                                                             mod PH  few PH few PH No Chg.                             B with                                                                              B & UR over                                                                          B & UR in                                                                            B with  B & UR B & UR                                     fine UR                                                                             85% of 2 patches                                                                            faint UR                                                                              just noted                                                                           starting                                   over 75%                                                                            coating                                                                              (15% of                                                                              just start-    over most                                  of coating   coating) only                                                                        ing            of coating                    2 day exposure                                                                             dense PH                                                                            dense #10                                                                            dense #10                                                                            dense PH                                                                              Dense #10                                                                            Dense  Dense #10                           and #10B                                                                            B & PH R                                                                             B & R in                                                                             B & R over                                                                            B & R over                                                                           #10 B+ B & R over                          +R over                                                                             over 100%                                                                            2 patches                                                                            100% of 100% of                                                                              R over 100% of                             100% of                                                                             of coating                                                                           with PH                                                                              coating coating                                                                              100% of                                                                              coating                             coating      B & R over            coating                                                 rest of                                                                       coating                                             __________________________________________________________________________     * = tack free, test A/test B                                                  PH = pinhole                                                                  B = blistering                                                                UR = under rust                                                               R = rust                                                                 

EXAMPLES, B-SERIES

Air-drying compositions are prepared from 80:20 blends of theunsaturated oil-modified resin of example 1A and the unsaturatedmelamine condensates of Examples 1-6 and 8. The compositions contain0.07 percent cobalt naphthenate and 0.045 percent maganese octoate.Coatings are prepared by applying the compositions to Bonderite 37 steelpanels and allowing them to air dry. Data for the evaluation of thecoatings are presented in Table 3. Taken with the data for the A Series,they show that increasing the allyl level of the unsaturated melamineresin causes (a) a decrease in aminoplast and formulation viscosity, (b)a decrease in formulation shelf life, and (c) an improvement incompatibility of the unsaturated melamine condensate and the unsaturatedvehicle. Increasing the acrylamide level of the UMF resin causes adecrease in coating tack free time and flexibility. Decreasing theallyl/acrylamide ratio causes the following properties to go through amaximum: rate of hardness development and final coating hardness,solvent resistance and QUV durability.

                                      TABLE 3                                     __________________________________________________________________________    Evaluation of Air-drying Unsaturated Compositions, B Series                              Ex.    Ex.    Ex.    Ex.   Ex.    Ex.   Ex.   Ex.                  Sample Number                                                                            1B     2B     3B     4B    5B     6B    8B    9B                   __________________________________________________________________________    Formulation App.                                                                         hazy   sl. hazy                                                                             hazy   v. hazy                                                                             hazy   sl. hazy                                                                            clear clear                Form. Visc. (cps)                                                                        1,900  1,800  2,300  2,300 2,300  2,300 800   7,000                Coating thick. (mm)                                                                      .033   .033   .033   .036  .033   .028  .028  .033                 Tack Free Time (min)                                                                     240/330                                                                              420/>600                                                                             180/330                                                                              225/340                                                                             170/300                                                                              250/450                                                                             400/>600                                                                            180/330              Hardness 1 day                                                                           4B     5B     6B     --    6B     5B    6B-5B 6B                   2 days     3B     3B-2B  5B     3B    4B-5B  --    --    6B                   4 days     HB     --     --     2B    --     3B    2B+   4B                   10 days    HB     HB-    B+     B     HB-    B     HB    B-                   21 days    F      HB     B+     HB-F  HB     B     HB    B                    MEK rubs 2 days                                                                          25     24     21     20    21     --    --    17                   4 days     35     --     --     30    --     16    35    22                   10 days    70     46     56     50    44     20    45    32                   21 days    120    95     95     60    83     37    65    48                   Water Spot 21 days                                                                       B      B      2B+    4B    B      --    --    3B-                  For. Impact 21 days                                                                      1.7    1.6    1.6    1.4   1.8    1.1   1.6   1.8                  QUV Durab. 21 days                                                            1 day Exposure                                                                           Yellow Yellow Yellow Yellow                                                                              Yellow Sl. Yellow                                                                          Med.                                                                                No chg.                                              UR just                                                                             sl. UR       + UR over                                                  starting           100% of                                                                       coating                    2 day Exposure                                                                           Dense #10                                                                            Dense #10                                                                            Dense #10                                                                            Dull  Dense #10                                                                            Dense #10   Dense #10                       B & UR in                                                                            B & UR in                                                                            B & UR over                                                                          UR over                                                                             B & UR over                                                                          B & R over  B & UR                                                                        over                            3 areas over                                                                         4 areas over                                                                         15%    85% of                                                                              20% of 80% of      25% of                          10% of 15% of of coating                                                                           coating                                                                             coating                                                                              coating     coating                         coating                                                                              coating                                                     4 day Exposure                                                                           Dense #9                                                                             Similar                                                                              Dense PH                                                                             Dense #10    Dense #10   Dense #10                       B & R in                                                                             to 2 days; +#10B+                                                                    B & R over                                                                           B + R +                                                                             +#9B+        B & R over                            15% of 20% of R over 100% of                                                                             UR over                                                                              R over      75% of                          coating                                                                              coating                                                                              35%    coating                                                                             25%    100% of     coating                                affected                                                                             of coating   of coating                                                                           coating                          __________________________________________________________________________

EXAMPLES, C-SERIES

Air-drying compositions similar to Examples 1B, 6B and 8B are preparedin which the weight ratio of oil-modified unsaturated resin tounsaturated melamine condensate is 65:35. Coatings are prepared byapplying the compositions to Bonderite 37 steel panels and allowing themto air-dry. Data for the evaluation of the coatings are presented inTable 4. They show that the compositions containing high levels ofmelamine condensate are substantially lower in viscosity than theunsaturated resin of example 9B. However, only the unsaturated melaminecondensate containing allyl and acrylamide units (Examples 1B, 1C) givesa significant improvement in hardness and solvent resistance withoutimpairment in tack free time or impact resistance. Indeed Example 1Cshows further improvement in solvent resistance and hence crosslinkdensity in comparison with Example 1B. Example 6C, containing themelamine acrylamide condensate shows decreased hardness in comparisonwith Example 6B and Example 8C containing the melamine allyl alcoholcondensate shows a substantial increase in the time necessary to reach atack free condition.

                                      TABLE 4                                     __________________________________________________________________________                Example                                                                            Example                                                                            Example                                                                            Example                                                                            Example                                                                             Example                                                                              Example                          Sample Number                                                                             1B   1C   6B   6C   8B    8C     9B                               __________________________________________________________________________    Formulation App.                                                                          hazy clear                                                                              sl. hazy                                                                           sl. hazy                                                                           clear clear  clear                            Viscosity, cps                                                                            1900 950  2300 1000 800   250    7000                             Coating Thickness (mm)                                                                    .030 .033 .028 .033 .028  .028   .029                             Tack free time (min)                                                                      270/300                                                                            285/360                                                                            270/480                                                                            285/480                                                                            390/>600                                                                            >600/>24 hr                                                                          240/360                          Hardness 1 day                                                                            2B   3B   5B   5B   5B    5B     5B                               4 days      HB   HB   3B   4B   2B    2B     2B                               12 days     HB   HB   B    3B   HB    HB     B                                21 days     F    F    B    3B   HB    HB     B                                MEK rubs 4 days                                                                           30   40   16   14   35    33     22                               12 days     80   125  20   19   45    60     40                               21 days     115  160  37   37   65    67     55                               Impact Resistance                                                             forward, joules                                                                           1.6  1.3  1.1  .9   1.6   1.6    1.5                              __________________________________________________________________________

EXAMPLE 10

An air-drying composition of 70 percent solids is prepared from asolution of an unsaturated oil-modified resin of oil length 32% sold byCargill under the tradename Alkyd 5700 and the unsaturated melaminecondensate of example 1 in a weight ratio of solids of 80:20. Thecomposition contains 0.07 percent cobalt neodecanoate and 0.03 percentLTD drier. The composition is coated on Bonderite 37 steel panels andallowed to air-dry. The coating is evaluated in comparison with acoating prepared from the alkyd resin alone (Example 11). The data areset forth in Table 5. Again the melamine-acrylamide-allyl alcoholcondensate in Example 10 improves the coating hardness, solventresistance and water resistance without adverse effect on the tack freetime and the impact resistance.

                  TABLE 5                                                         ______________________________________                                                            Example    Example                                        Sample Number       10         11                                             ______________________________________                                        Compatibility       clear      clear                                                              red-orange orange                                         Viscosity           420 cps    450 cps                                                            thin skin 5d.                                             Pot. life Viscosity @ 21 days R.T.                                                                480 cps    450 cps                                        Thickness mm.       0.028-.036 0.030-0.033                                    Appearance          Hi gloss   Hi gloss                                                           colorless  colorless                                      Tack Free Time mins.(touch/Al foil)                                                               275/375    225/490                                        Hardness 0.038 mm.                                                            (1 day)             <<6B       <<6B                                           (4 days)            3B         <6B                                            (5 days)            HB         4B                                             (11 days)           HB-F       4B                                             (21 days)           HB-F       4B-5B                                          MEK rubs (4 days)   36         16                                             (11 days)           63         19                                             (21 days)           70         17                                             Water Spot (5 days) ↓B-2B                                                                             ↓6B                                     (11 days)           ↓2B+                                                                              ↓6B                                     Forward Impact (21 days), joules                                                                  1.2        1.2                                            ______________________________________                                    

What is claimed is:
 1. An unsaturated condensate of analkoxymethylmelamine, an allylic alcohol, and an acrylamide, wherein thealkoxymethylmelamine has a combined ratio of formaldehyde to melamine inthe range of about 5:1 to about 6:1 and a combined ratio of etherifyingalcohol to melamine in the range of about 4.7:1 to about 6:1, whereinthe alkoxymethyl groups of the unsaturated condensate contain C₁ to C₁₀alkoxy groups, wherein the acrylamide is represented by the formula:##STR3## wherein R₁ and R₂ are selected from the group consisting ofhydrogen and methyl, wherein the allyl alcohol is represented by theformula: ##STR4## wherein R₃ is hydrogen or a C₁ to C₄ alkyl group,wherein the ratio of allylic alcohol moieties to acrylamide moieties inthe condensate is in the range of about 3:1 to about 1:3, wherein thecondensate contains at least about 0.75 allylic moieties and no morethan about 3 acrylamide moieties per melamine ring and wherein the totalof allylic moieties and acrylamide moieties of the condensate is in therange of about 2 to about 4 per melamine ring.
 2. The unsaturatedcondensate of claim 1, wherein the alkoxymethylmelamine ismethoxymethylmelamine.
 3. The unsaturated condensate of claims 1 or 2,wherein the allylic alcohol is allyl alcohol or methallyl alcohol. 4.The unsaturated condensate of claims 1 or 2, wherein the allylic alcoholis allyl alcohol.
 5. The unsaturated condensate of claims 3 or 4,wherein R₁ and R₂ are hydrogen.
 6. The unsaturated condensate of claim 1wherein the condensate contains about 1 to about 3 allyl groups and fromabout 1 to about 2 acrylamido groups per melamine ring.
 7. Theunsaturated condensate of claim 6, wherein the alkoxymethylmelamine is amethoxymethylmelamine.
 8. The unsaturated condensate of claim 1 whereinthe condensate contains about 1.5 to about 2.5 allyl moieties and about1 to about 2 acrylamide moieties per melamine ring.
 9. The unsaturatedcondensate of claim 8, wherein the alkoxymethylmelamine is amethoxymethylmelamine.
 10. A process for the preparation of anunsaturated condensate of an alkoxymethylmelamine, an allylic alcohol,and an acrylamide which comprises reacting the acrylamide with thealkoxymethylmelamine at a temperature below about 120° C. until thereaction is substantially complete and reacting theacrylamide--alkoxymethylmelamine condensate with the allylic alcohol ata temperature in the range of about 80° to about 110° C. in the presenceof a catalytic quantity of an acid catalyst and apolymerization-inhibiting quantity of an inhibitor, wherein thealkoxymethylmelamine has a combined ratio of formaldehyde to melamine inthe range of about 5:1 to about 6:1 and a combined ratio of etherifyingalcohol to melamine in the range of about 4.7:1 to about 6:1, whereinthe alkoxymethyl groups of the unsaturated condensate contain C₁ to C₁₀alkoxy groups, wherein the acrylamide is represented by the formula:##STR5## wherein R₁ and R₂ are selected from the group consisting ofhydrogen and methyl, wherein the allyl alcohol is represented by theformula: ##STR6## wherein R₃ is hydrogen or a C₁ to C₄ alkyl group, andwherein the condensate has a ratio of allylic moieties to acrylamidemoieties in the range of about 3:1 to about 1:3, the total of allylicmoieties and acrylamide moieties being in the range of about 2 to about4.0 per melamine ring, at least 0.75 being allylic moieties and not morethan 3 being acrylamide moieties.
 11. The process of claim 10 whereinthe alkoxymethylmelamine is a methoxymethylmelamine, the allylic alcoholis allyl alcohol and the acrylamide is acrylamide.
 12. The process ofclaims 10 or 11, wherein the catalyst is an acid of pKa less than about3.